Rumble strip
Rumble strips may also be installed in a series across the direction of travel, to warn drivers of a stop or slowdown ahead, or of an approaching danger spot.
[5] There are several different ways to install rumble strips: Surface-mount raised pavement reflectors are easily scraped off by the blade on snowplows, and thus are not practical in many locations in the United States and Canada.
The scoring in the pavement—at the dual-lane divisions—reflected drivers' headlights, while "the resonant whine or roar coming off the ridges as the vehicle's tires rolled over the strip let the motorist know he was getting out of his traffic lane."
With the "singing lane" safety benefit recognized for nearly a decade, the New Jersey chair of its Highway Authority, Ransford J. Abbott, mandated pavement-edge scoring for the Garden State Parkway in the early 1950s.
The development of ceramic and plastic raised systems enabled installation on concrete pavement highways, and the smaller footprint was better suited for the dashed centerline.
[11] A US Federal Highway Administration (FHWA) sponsored study stated that driver inattention comes in many forms, including distraction, daydreaming/competing thoughts, fatigue/drowsiness, and alcohol/drug impairment.
[24] Note that in the KATU.com article photograph (in the upper left-hand corner) of the crash scene, the passenger-side tire print in the soft shoulder that suggests that all four wheels passed over the rumble strip before the driver attempted the unsuccessful recovery.
The FHWA states: "Long sections of relatively straight roadways that make few demands on motorists are the most likely candidates for the installation of shoulder rumble strips."
Implied in this statement is that highways that are twisty and hilly with a variable foreground have low rates of accidents due to inattention, and are therefore not likely candidates for the installation of rumble strips.
In addition, safety improvements are not linear; there are diminishing marginal returns with a safer driver population, in which it is more difficult to further reduce the accident rate.
[17] Almost all before-and-after studies are based on Interstate (freeway, turnpikes, thruways) test sites have minimum 12-foot (3.7 m) paved shoulders and very high crash rates due to inattention.
The collision reduction attributed to the installation of CSRS is mainly a function of stable shoulder width, crash rate and profile, climate and diminishing marginal returns.
A 2005 National Cooperative Highway Research Program (NCHRP) study concluded that overall motor vehicle crashes at sites treated with Centerline Rumble Strips were reduced overall by 14%.
A 2007 Minnesota study concluded that while transverse rumble strips offer a low cost and easy-to-install option, they “did not seem to be successful at reducing approach speeds at the project sites”.
The 2003 Texas indicated: "The majority of studies found reported large reductions (40% to 100%) of accidents after installing transverse rumble strips.
"[7] In Ghana, rumble strips running across the entire carriageway were installed at Suhum Junction on the main Accra-Kumasi highway and reduced crashes by about 35% and fatalities by about 55%.
"[44] A 2009 FHWA intelligent systems study suggested that a combined infrastructure-based and in-vehicle warning could be highly effective in reducing crossing path crashes and fatalities at signalized intersections.
In certain situations, such as an engaging single-lane highways that typically have narrow shoulders, high precipitation, in a northern climate with frequent freeze-thaw cycles, rumble strip effectiveness may be negative.
"[35] Also, as lane departure warning systems built into vehicles become more widespread, the physical CSRS, CRS, and CLRS in pavements may become increasingly redundant.
[46] The 2003 Montana study stated that in certain cases, the rumble strips may act only as a warning of an impending crash, and that sort of a situation is much more likely where less shoulder is available for recovery.
Generally, air turbulence and vibration from passing large trucks keep rumble strips clear of debris and ice, but this process may take several days.
[48] In February 2010, Johnson County, Kansas, considered legislation to allow buses to travel on the paved shoulder (which was rumble stripped) when traffic slows to less than 35 mph (56 km/h).
[50][51][52] Some residents living close to either newly installed lane or transverse rumble strips have complained about noise levels and were successful in having them removed at considerable expense.
[53] In 2005, the London borough of Bromley removed transverse rumble strips after residents complained of the excessive "machine gun fire" noise.
Studies show that rumble strips terminated approximately 200 m (660 ft) away from residential or urban areas produce tolerable noise impacts on residences.
[67] A 2005 Quebec study concluded: "Based on the results of the analyses, it was not possible to recommend a type of rumble strip that would provide sufficient warning to drivers who encroach on the shoulder while remaining safe for cyclists who ride over it.
Center-line rumble strips are a concern for cyclists as well, as motorists are less inclined to cross the centerline to provide sufficient space when passing bicyclists.
[62][63][64][65] In 2009 in St. Joseph County, Michigan (US), after a lobbying campaign by the local Amish community, a new $20,000 rumble strip installation was removed at a cost of $275,000 to the taxpayers.
Wildlife-vehicle collisions can be a significant problem when large animals are involved such as moose, elk, and deer, which can cause serious vehicle damage, injury, and fatalities.
Loose rock salt in the rumble strip subjected to evaporating moisture will cake and accumulate and is not easily dislodged by truck traffic.
